File:Image from page 109 of "Water reptiles of the past and present" (1914) (14586358679).jpg

Identifier: waterreptilesofp1914will Title: Water reptiles of the past and present Year: 1914 (1910s) Authors: Williston, Samuel Wendell, 1851-1918 Subjects: Aquatic reptiles Publisher: Chicago, Ill., The University of Chicago Press Contributing Library: Boston Public Library Digitizing Sponsor: Boston Public Library

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Text Appearing Before Image: aving abouttwenty vertebrae in thelongest-necked forms;the body is moderatelylong, and broad, andthe tail is relativelyshort. The vertebraeand ribs are quite likethose of the plesiosaurs,that is, the vertebraeare gently concave ateach end, and the dorsal ribs are attached by a single head to thetransverse process high up on the arch; the cervical ribs are double-headed, precisely like those of the older plesiosaurs, one of the char-acters which insistently provesthe relationships of the twogroups. The bones of the shoul-ders (Fig. 46) also have manyresemblances to the extraor-dinary ones of the plesiosaurs,though they are much lessspecialized. There was nosternum; the coracoids arelarge, though very muchsmaller than those of the plesi-osaurs. The collar-bones are large and strong, joining each otherin front of the coracoids and firmly united with the shoulder-blades at the outer extremity. Four vertebrae are united to forma sacrum, and their union with the hip bones (Fig. 47) was much

Text Appearing After Image: Fig. 47.—Pelvic bones of Nothosaurus:il, ilium; ac, acetabulum; p, pubis; is,ischium. (After Andrews.) SAURO PTERYGIA 99 firmer than was the case with the plesiosaurs. The limbs areelongated, but it will be observed in the figures (Fig. 48) that theradius and ulna, tibia and fibula, that is, the bones of the forearmand of the leg proper, are relatively very short as compared withthe humerus and femur, a sure indication of the beginning ofaquatic habits. The toes and fingers were doubtless webbed, andthere was no increase in the num-bers of bones in the digits, soconspicuous in the plesiosaurs.The external nostrils are large, butare not situated so far back nearthe eyes as in the plesiosaurs.There is a large pineal opening inthe top of the skull, as in the plesi-osaurs, but no sclerotic or bonyplates have been observed in theeyes. They had ventral ribs likethose of the plesiosaurs. No impressions of scales orbony plates have ever been foundwith the remains of the notho-saurs, and it

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